Process and apparatus for producing glass fibers

ABSTRACT

A process and an apparatus for producing glass fibers by centrifugal force are provided. Molten glass is fed into a hollow cylinder of rotating member which rotates at high speed by means of a driving device and is heated. The molten glass is ejected to an outside of a peripheral wall by centrifugal force generated by high speed rotation of the rotating member through orifices, each of which has different diameter, and which are provided alternately in a circumferential direction of the peripheral wall. A primary steam of molten glass is ejected. The primary streams is introduced into flame flow ejecting from drawing burners located at outside of the peripheral wall to form secondary fibers. A compressed gas flow is ejected to a direction at an acute angle through an ejecting outlet of an ejecting nozzle to collide the compressed fluid with the secondary fibers to thereby produce glass fibers by continuously.

FIELD OF INVENTION

The present invention relates to a process and an apparatus forproducing glass fibers by utilizing centrifugal force, which can improvethe production efficiency, can lower the fuel consumption by drawingburners, and can continuously spin glass fibers capable of complyingwith quality requirements for glass fiber products by using a simplemeans for production.

PRIOR ART

A process and an apparatus for producing glass fibers by centrifugalforce have been disclosed in JP-B-42-13748 and U.S. Pat. No. 4,689,061.JP-B-42-13748 discloses that a rotating member has a peripheral wallwhich is provided with orifices in a longitudinal direction. Thediameter of orifices becomes smaller in a direction from the upper sideto the bottom side, in order to solve disadvantage that glass fiberswith good quality cannot be produced due to collision of fibers in theupper side and fibers in the lowerside when applying wind flow to finestrings of a material ejected through the orifices by centrifugal force.

Whereas, the apparatus disclosed in U.S. Pat. No. 4,689,061 isconstituted by arranging in plurality of rows of orifices, whereorifices in 2 or more rows are provided by perforation in a verticaldirection, in the peripheral wall of a rotating member, providingno-orifice part at the middle part between the orifices in rows, andarranging the orifices of which diameter in the upper side being smallerthan the diameter of the orifices in the lower side.

However, according to the processes as disclosed in the above formerprior art, it is not possible to obtain glass fibers with good quality,because the collision of fibers cannot be prevented during the processof drawing of fine strings of a material ejected through the orifices tofine fibers, if orifices in 40 rows more or less are arranged in avertical direction in order to improve the production efficiency per arotating member. Furthermore, as various types of glass fibers arerequired, such as low density product required for having restoringproperty against compression and medium-high density product requiredfor having hardness, there is a limit for such process in the productionof glass fibers complying with each requirements for the quality, suchas fiber diameter, fiber diameter distribution and fiber length.

The process disclosed in the later patent is constituted by providingthe non-orifice part in the middle between the orifices in rows.Therefore, if the number of the orifices are increased for improving theproduction capacity per a rotating member, it is required to increasethe height of the peripheral wall of the rotating member to oversize,thus increasing fuel consumption by burners required for producing finefibers to raise the production cost and causing more collision of thefibers, which thereby makes difficult to obtain glass fibers with goodquality.

SUMMARY OF INVENTION

Considering the prior arts as described above, it is an object of thepresent invention to provide a process and an apparatus for producingglass fibers with good quality that complies with requirements forvarious glass fiber products in terms of fiber diameter, fiber diameterdistribution, fiber length, etc., characterized by increasing the numberof orifice rows provided by perforation in the peripheral wall of therotating member and arranged in a vertical direction to increase theproduction capacity per a rotating member, and allowing to provideadvantages of reducing fuel consumption by burners used for drawing theejected streams to minimize the production cost.

According to the present invention, it is provided a process forproducing glass fiber comprising heating and rotating a hollowcylinder-shaped rotating member having peripheral wall provided withorifices so as to rotate molten glass in the rotating member, andejecting the molten glass through orifices by centrifugal force to formglass fiber, characterized in ejecting molten glass through at least twotypes of orifices arranged alternately in a circumferential direction ofthe rotating member, each of said two types of orifices having differentdiameter, so as to form at least two types of primary streams havingdifferent length; introducing said primary streams into flame flowaround the rotating member, said flame flow being ejected in a directionsubstantially parallel with a generatrix direction of an outercircumference of the peripheral wall, so as to fine said primary streamsto form secondary fibers; and ejecting compressed fluid in a directionat an acute angle relative to the flame flow including secondary fibers,to collide the secondary fibers with the compressed fluid.

Preferably, the compressed fluid is ejected in an angle of 15-30 degreerelative to the generatrix direction of the outer circumference of theperipheral wall of the rotating member.

Preferably, a distance between a top edge of the compressed fluid and aa bottom edge of the peripheral wall of the rotating member is at least30 mm.

Also, according to the present invention, it is provided an apparatusfor producing glass fiber comprising a hollow cylinder-shaped rotatingmember having a peripheral wall alternately provided with at least twotypes of orifices each having different diameter in a circumferentialdirection of the peripheral wall; a circular drawing burnerconcentrically arranged above and around the rotating member, and havingan ejecting outlet opened in substantially parallel with a generatrixdirection of an outer circumference of the peripheral wall; and anejecting nozzle around the drawing burner, said ejecting nozzle beingconcentrically arranged above and around the peripheral wall of therotating member, and having an ejecting outlet opened in a direction atan acute angle relative to the generatrix direction of the outercircumference of the peripheral wall.

Preferably, at least two types of orifices each having differentdiameter are alternately provided in the peripheral wall in thecircumferential direction of the peripheral wall, to form a latitudinalrow; a plurality of longitudinal orifice rows are provide in theperipheral wall in the generatrix direction of the outer circumferenceof the peripheral wall; and the orifice in a lowerside region has adiameter smaller than that of the corresponding orifice in an upper sideregion.

Preferably, the peripheral wall is provided with larger orifices andsmaller orifices; the larger orifices are arranged in the generatrixdirection of the outer circumference to form first bands group oforifices; the smaller orifices are arranged in the generatrix directionof the outer circumference to form second bands group of orifices; andthe first bands group of orifices and the second bands group of orificesare arranged alternately in the circumferential direction of theperipheral wall (2) of the rotating member.

Preferably, the orifice arranged in a lowerside region has a diametersmaller than that of the orifice arranged in an upper side region ineither the first bands group of orifices or the second bands group oforifices.

Preferably, a difference in the diameter between at least two types oforifices each having different diameter is in a range of from 0.02 to0.3 mm.

BRIEF EXPLANATION FOR DRAWINGS

FIG. 1 is a cross section showing main parts of an apparatus accordingto the present invention.

FIG. 2 is an example for an arrangement of orifices.

FIG. 3 is an example for another arrangement of orifices.

FIG. 4 is a schematic diagram showing a process to introduce primarystreams into flame flow.

FIG. 5 is a schematic diagram showing an ejection of compressed fluidflow.

FIG. 6 is a chart showing a relationship between glass temperature andviscosity.

FIG. 7(a) is a chart showing a fiber diameter distribution of lowdensity product, and FIG. 7(b) is a chart showing a fiber diameterdistribution of medium-high density product.

PREFERABLE EMBODIMENT FOR CARRYING OUT THE INVENTION

FIG. 1 and FIG. 2 show an example for an apparatus according to thepresent invention. The apparatus for producing glass fibers according tothe present invention comprises a hollow cylinder-shaped rotating member1, a drawing burner 9 circumferentially arranged above the rotatingmember 1, and ejecting nozzles 12. In the apparatus shown in FIG. 1, aglass melting furnace 4 and a forehearth 5 are arranged above therotating member 1. The forehearth 5 is provided with an ejecting nozzle6 on a lower surface thereof. Molten glass is fed through the ejectingnozzle 6 to an inside of the hollow cylinder of the rotating member 1.

The rotating member 1 has a peripheral wall 2 which is provided with aplurality of orifices. FIG. 2 shows an example of an arrangement of theorifices provided by perforation in the peripheral wall 2 of therotating member 1. In a circumferential direction of the peripheral wall2, the peripheral wall is provided with latitudinal rows of orifices.Each of the latitudinal rows comprises larger orifices (orifices with alarger diameter) 31 and smaller orifices (orifices with a smallerdiameter) 32 which are arranged alternately with a certain interval. Ina generatrix be direction of the peripheral wall, the peripheral wall isprovided with longitudinal a rows of orifices. A larger orifice 31 inone of the latitudinal rows is arranged between the larger orifice 31and the smaller orifice 32 in the adjacent of the latitudinal row. Eachof large orifices 31 a in latitudinal rows arranged on an lowerside hasa smaller diameter than that of larger orifices 31 in latitudinal rowsarranged on an upper side. In the illustrated example shown in FIGS. 1and 2, each of the latitudinal rows comprises two types of orificeshaving different diameter, however, such row may be comprises 3 or moretypes of orifices having different diameter.

A driving device (not shown) for rotating the rotating member 1 rotatesa belt 7, and the belt 7 is connected with a rotating shaft 8, so as torotate the rotating member 1 connected to the shaft 8 at high speed. Thedrawing burner 9 is concentrically and circumferentially arranged abovethe rotating member 1. The drawing burner 9 has an ejecting outlet 10and a combustion room 11. The outlet 10 opens downwardly insubstantially parallel with an outer circumference of the peripheralwall 2, and flame flow G of burned exhaust gas in the combustion room 11ejects from the drawing burner 9 along with the generatrix direction ofthe peripheral wall 2.

Ejecting nozzles 12 for the compressed fluid are arranged concentricallywith an outer circumference of the rotating member 1, below thecombustion room 11, and around the ejecting outlet 10 of the drawingburner 9. Each of the ejecting nozzles 12 is provided with an ejectingoutlet 13 which is opened in a direction at an acute angle relative tothe generatrix direction of outer circumference of the rotating member1. In prior arts, such ejecting nozzle 12 has not been employed. Thenumeral 14 in FIG. 1 indicates a burner for heating an inside of therotating member 1.

The rotating member 1 rotates at high speed by the driving device, theinside of the rotating member 1 is heated by the burner 14, and themolten glass B is fed through the ejecting nozzle 6 into the inside ofthe hollow cylinder of the rotating member 1. The molten glass B isejected out though the ejecting nozzle 6 of the forehearth 5 in atapered cylindrical form, then is fed into the inside of the rotatingmember 1 in linear state.

The molten glass B fed into the inside of the rotating member 1 israised upwardly onto an internal surface of the peripheral wall 2 by acentrifugal force generated by rotation of the rotating member 1 at highspeed, and is ejected through a plurality of larger orifices 31 (31 a)and smaller orifices 32 (32 a) of the peripheral wall 2, to form alarger primary stream having larger diameter obtained through the largerorifices 31 (31 a) and a smaller primary stream having smaller diameterobtained through the smaller orifices 32 (32 a). The larger primarystream has greater mass, while the smaller primary stream has less mass.Consequently, when equivalent kinetic energy (namely the centrifugalforce generated by the rotating member 1) is applied, the larger primarystreams 311 are spread in longer distance than the distance for theshorter primary streams 312 (See FIG. 4). Thus, a length of the primarystream ejected through the larger orifices 31 (31 a) is longer than thatof the primary stream ejected through the smaller orifices 32 or 32 a.

The process and the apparatus according to the present invention areconstituted as described above, at least two types of orifices eachhaving two different diameter are alternately provided in onelatitudinal row circumferentially extending in peripheral wall 2 of therotating member 1. In other word, a larger orifice 31 is adjacent to twosmaller orifices 32, and a smaller orifice 32 is adjacent to two largerorifices 31. The primary stream formed by the ejection through anorifice 31 (or 32) by the centrifugal force of the rotating member 1 hasa different length from the length of another primary stream formed bythe ejection through the adjacent orifice 32 (or 31), and these adjacentprimary streams, each of those which has a different length, areintroduced into flame flow fed from the drawing burner. Therefore, asshown in FIG. 4, there is no opportunity for the adjacent primarystreams 311 and 312 to be knotted or clashed, and these streams canefficiently receive heat and drawing load given by the flame flow.

Each of the orifices 31 a and 32 a in a latitudinal row positioning atthe lowerside of the generatrix direction of the outer circumferencerespectively has a a diameter smaller than that of the correspondingorifices 31 and 32 in a latitudinal row at the upper side of thegeneratrix direction. Thus, the primary stream ejected through the upperside orifice and the primary stream ejected through the lowersideorifice do not clash each other. A distance between one orifice and theadjacent orifice in both the circumferential and generatrix directionscan be the same as that of prior arts. Therefore, according to thepresent invention, no problem shall be raised in terms of reduction inproduction capacity and the need for the increase of the height of theperipheral wall.

FIG. 3 shows an example for another arrangement of rows of the orificesprovided by perforation in the peripheral wall 2. Each of the oddlatitudinal rows, such as the first row, the third row, etc. locatedfrom the upper side of the generatrix direction of the outercircumference of the peripheral wall 2, has larger orifices 31 andsmaller orifices 32. The corresponding larger orifices 31 in the oddrows are aligned in the same generatrix direction, and the correspondingsmaller orifices 32 in the odd rows are also aligned in the samegeneratrix direction. On the other hand, each of the even latitudinalrows, such as the second row, the fourth row, etc. has larger orifices31 and smaller orifices 32. Each of the orifices 31 and 32 in even rowsare positioned in a middle between an orifice 31 and an orifice 32 inthe odd row. Accordingly, the peripheral wall 2 is formed alternatelywith a longitudinal orifice row group X comprising two rows of thelarger orifices 31, and the other longitudinal orifice row group Ycomprising two rows of the smaller orifices 32 in the generatrixdirection. Diameters of the orifices 31 a and 32 a positioning at thelowerside of the generatrix direction are smaller than those of orifices31 and 32 positioning at the upper side of the generatrix direction,like the example shown in FIG. 2. The arrangement of the rows should notbe limited to the examples shown in FIG. 2 and FIG. 3, and other variousarrangements may be applied to the present invention. In this regard, itis essential that 2 or more types of orifices each having differentdiameter are provided in the outer circumferential direction of theperipheral wall 2, and that the diameter of the orifice positioning atthe lowerside of the generatrix direction is smaller than the diameterof the orifice positioning at the upper side of the generatrixdirection.

Around the peripheral wall 2 of the rotating member 1, flame flow G isejected from the ejecting outlet 10 located around the rotating member 1toward a direction in approximately parallel with the generatrixdirection of the outer circumference of the peripheral wall 2. Theprimary stream is introduced into the flame flow G, and is then madeinto a fine fiber to form a secondary fiber. FIG. 4 is a diagramexplaining the process for introducing the primary stream into the flameflow G according to the present invention. In FIG. 5, the primary streamejected through orifices of latitudinal rows on the upper side and theprimary stream ejected through orifices of latitudinal row on thelowerside are introduced into the flame flow G having a width (a), andmaintain a certain distance (b) therebetween in the flame flow. Thus,these primary stream can be subjected to be efficiently heated by theflame flow and to be efficiently drawn, so as to be made into finefibers.

The secondary fibers being made into fine fibers are cut by collidingwith compressed fluid ejected through the ejecting outlet 13 of theejecting nozzle 12. In the illustrated example, the compressed fluid isejected through the ejecting outlet 13 at high speed as much as 3 kg/cm²on pressure basis. In this case, the angle of the ejection is preferablyabout 15-30 degree relative to a flowing direction of the flame flow G.When cutting the secondary fibers by applying the compressed fluid tothe secondary fibers, the length of the secondary fibers can becontrolled by appropriately selecting the angle to eject the compressedfluid and ejecting pressure.

In the collision or impact of the secondary fiber and the compressedfluid, it is required that a temperature at a bottom edge R of theperipheral wall 2 is not lowered due to the ejecting flow S of thecompressed fluid, and that the bottom edge R of the peripheral wall 2does not affect the performance to make the secondary fibers finer.Thus, a distance L between the bottom edge R of the peripheral wall 2and a top edge P of the compressed fluid S should be about 30-50 mm ormore, so as to prevent the top edge P of the compressed fluid S to thebottom edge R of the peripheral wall 2 of the rotating member 1. Thus,the lowering of the temperature at the bottom edge of the peripheralwall 2 due to collision by the compressed fluid flow S may be prevented.

According to the present invention, the angle α of the ejectingdirection of the compressed fluid is about 15-30 degree, and thedistance L between the bottom edge R of the peripheral wall 2 and thetop edge P of the compressed fluid S is at least about 30-50 mm.Therefore, the temperature of the peripheral wall 2 does not decrease.In addition, since the ejecting flow S collides with the flame flow Gafter the primary stream is fined, it does not affect the formation offine fibers, so as to continuously produce the secondary fibers withappropriate fiber length.

The preferable fiber length can be obtained by controlling the ejectedforce of the compressed fluid. Generally, it is preferable to control oradjust the fiber length longer in case of low density product to whichrestoring property from compressed state is required, and it ispreferable to control or adjust the fiber length shorter in case ofmedium-high density product to which hardness and rigidity is required.

When the rotating member 1 has the diameter of is 400 mm, it ispreferable to provide 20-30 ejecting nozzles 12 in the apparatus. Ifless than 20 of the ejecting nozzles 12 is provided, the fiber lengthtends to be unfavorably longer. When more than 30 of the ejectingnozzles 12 are provided, no remarkable effect to obtain shorter fibersis given, but consumption of the compressed fluid is increased tothereby make the production cost unfavorably high. The ejecting outlet13 to be used is provided in slot-shaped, of which shorter side lengthis 0.4-1.0 mm and the longer side length is 7-15 mm, and preferably theone having the dimension of 0.5 mm×10 mm. If the size of the slot-shapedejecting nozzle is smaller than the one as described above, the fiberlength tends to be unfavorably longer. When the size of a the ejectingnozzles is larger than the one as described above, no remarkable effectmay be obtained, but consumption of the compressed fluid is increased tothereby make the production cost unfavorably high.

According to the process specified in the present invention, glassfibers were produced by using standard glass and hard glass as thematerial, respectively, under the condition as specified in Table 1. Forexample, For producing glass fibers by using standard glass, thediameter of the larger orifice 31 was 0.9 mm, the diameter of thesmaller orifice 32 was 0.75 mm, the diameter of the larger orifice 31 awas 0.8 mm, and the diameter of the smaller orifice 32 a was 0.7 mm. Sixlatitudinal rows comprising the larger orifices 31 and the smallerorifices 32 were formed, while 40 latitudinal rows comprising the largerorifices 31 a and the smaller orifices 32 a were provided. Although thediameter of the orifices provided on the upper side and the diameter ofthe orifices provided on the lowerside are altered to be smaller step bystep in this example, the present invention includes an embodiment inwhich the diameters of the orifices gradually become smaller from theupper side to the lowerside.

For comparison, glass fibers were prepared according to the conventionalprocess under the condition described in Table 1 by using standard glassand hard glass as the material, respectively.

“Standard glass” is defined as boric acid-containing (B₂O₃) glass orboric acid-free glass, which has a viscosity of approximately 1,000poise at 1,070° C. as shown in FIG. 6. “Hard glass” is defined as boricacid-containing (B₂O₃) glass or boric acid-free glass, which has aviscosity of approximately 1,000 poise at 1,200°.

A low density glass fiber molding having the dimension of 10 Kg/m³×50mm×430 mm×1370 mm (which may be used for an insulating article) wasproduced by molding the glass fibers obtained as described above.Further, the restoring rate of said insulating article was measured. Therestoring rate was measured as follows. The insulating article wascompressed to 87% in a volume, and was maintained in the compressedstate for a month. The compression was released, and after 4 hours athickness of the insulating article was measured. A ratio of themeasured thickness relative to a required thickness (50 mm) was obtainedto obtain the restoring rate.

TABLE 1 Standard Glass Hard Glass Low Density Present Present Productinvention Prior Art invention Prior Art Spinning 400 400 400 400 Amount(Kg/Hr) Height of 71 58 71 58 peripheral wall (mm) Fuel Gas 14 17 14 17Amount (m³/Hr) Average Fiber 6.5 7.0 7.5 7.5 Diameter (μm) Restoringrate 115 110 110 105 against Compression (%) Energy Index 35 42.5 3542.5 (Fuel gas amount/ Spinning a- mount: m³/ton) Ejection Pres- 1.5 02.0 0 sure of Ejecting Nozzl (Kg/ cm²) Fiber Length Somewhat LongSomewhat Long short short Orifice ◯ ∘ ◯ ∘ ∘ ∘ ∘ ∘ ∘ ◯ ∘ ◯ ∘ ∘ ∘ ∘ ∘ ∘Arrangement  ◯ ∘ ◯  ∘ ∘ ∘ ∘ ∘  ◯ ∘ ◯  ∘ ∘ ∘ ∘ ∘ ◯ ∘ ◯ ∘ ∘ ∘ ∘ ∘ ∘ ◯ ∘ ◯∘ ∘ ∘ ∘ ∘ ∘  ◯ ∘ ◯  ∘ ∘ ∘ ∘ ∘  ◯ ∘ ◯  ∘ ∘ ∘ ∘ ∘ ◯ ∘ ◯ ∘ ∘ ∘ ∘ ∘ ∘ ◯ ∘ ◯∘ ∘ ∘ ∘ ∘ ∘ (Orifice (Orifice Arrangement Arrangement in FIG.3) in FIG.3) Upper Upper 6 Upper 6 Upper 6 6 Rows Rows 0.9 Rows Larger Rows 1.0Larger ori- mm orifice dia- mm fice dia- meter 0.85 meter: 0.9 mm mmSmaller ori- Smaller fice dia- orifice meter: 0.75 diameter: mm 0.85 mmRemaining Remaining Remaining Remaining 40 Rows 31 Rows 40 Rows 31 RowsLarger 0.8 mm Larger 0.9 mm orifice orifice diameter: diameter: 0.8 mm0.9 mm Smaller Smaller orifice orifice diameter: diameter: 0.7 mm 0.8 mm

As can be seen from Table 1 shown above, the consumption of fuel whenusing the equivalent amount of glass fibers in the present invention isless than that in the prior art. In the present invention, thecompressed fluid is ejected from the ejecting nozzle 12 to collide it tothe secondary fibers. At this stage, the secondary fibers are notknotted or entangled with each other and are distributed, because thelength of the obtained fibers according to the present invention areshorter than those obtained by the prior art. In the example of thepresent invention, the ejection pressure of the ejecting nozzle was 1.5kg/cm² for standard glass and 2.0 kg/cm² for hard glass, becausevoscocity of glass was considered.

The difference in diameter between the larger orifice 31 and the smaller6, orifice 32 both provided in the peripheral wall 2 of the rotatingmember 1 is fixed to a range of from 0.02 to 0.3 mm (including the casefurther larger or shorter orifices are provided). When the difference isless than 0.02 mm, there is no substantial a difference in the length ofthe primary stream to be ejected. When the difference exceeds 0.3 mm,the difference in the spinning amount between the larger orifice and thesmaller orifice becomes too big, because the spinning amount(g/orifice/Hr) through one orifice increases relative to the valueobtained by raising the orifice diameter to 4th power, and therefore, itis not possible to produce glass fibers with good quality under the samecondition (such as condition as to drawing burner, hollow rotatingmember, molten glass, ejecting nozzle, etc.). From the reason describedabove, the difference in the diameter between at least two differenttypes of orifices each having different diameter is fixed to a range offrom 0.02 to 0.3 mm. In the example described above, the diameter of thelarger orifices arranged in the upper region is fixed to 0.9 mm, whilethe diameter of the smaller orifices arranged in the upper region isfixed to 0.75 mm, and the difference in these diameters is 0.15 mm, incase of the standard glass.

According to the present invention, glass fibers were prepared under thecondition described in Table 2 by using standard glass and hard glass asthe material, respectively. For comparison, according to theconventional invention, glass fibers were also prepared under thecondition described in Table 2 by using standard glass and hard glass asthe material, respectively. These standard glass and hard glass are thesame ones as used in the example (and comparative example) conditionedin Table 1.

Medium-high density glass fiber moldings having the dimensions of 32Kg/m³×50 mm×605 mm×910 mm and 96 Kg/m³×50 mm×605 mm×910 mm (which areused as an insulating article) were produced by molding the glass fibersobtained as described above. Also, each of the thus obtained insulatingarticles was compressed so as to be reduced to the 50% by volume tomeasure the compressive strength thereof.

TABLE 2 Middle-high Standard Glass Hard Glass Density Present PresentProduct invention Prior Art invention Prior Art Spinning A- 400 400 400400 mount (Kg/Hr) Height of 71 58 71 58 peripheral wall (mm) Fuel Gas A-14 17 14 17 mount (m³/Hr) Average Fiber 6.5 7.0 7.5 7.5 Diameter (μm)Compressive Strength at 50% Compres- sion (Kg/m³) 32 kg/m³ Fiber 1200800 1100 700 96 kg/m³ Fiber 10100 8500 9500 7900 Energy Index 35 42.5 3542.5 (Fuel gas amount/Spin- ning amount: m³/ton Ejection Pres- 2.2 0 2.80 sure of Ejecting Nozzle (Kg/ cm²) Fiber length Short Long Short LongOrifice ◯ ∘ ◯ ∘ ∘ ∘ ∘ ∘ ∘ ◯ ∘ ◯ ∘ ∘ ∘ ∘ ∘ ∘ Arrangement  ◯ ∘ ◯ ∘  ∘ ∘ ∘∘ ∘  ◯ ∘ ◯ ∘  ∘ ∘ ∘ ∘ ∘ ∘ ◯ ∘ ◯ ∘ ∘ ∘ ∘ ∘ ∘ ◯ ∘ ◯ ∘ ∘ ∘ ∘ ∘  ∘ ◯ ∘  ∘ ∘∘ ∘ ∘  ∘ ◯ ∘  ∘ ∘ ∘ ∘ ∘ (Orifice (Orifice Arrangement Arrangement inFIG. 2) in FIG. 2) Upper 6 Upper 6 Upper 6 Upper 6 Rows Larger Rows 0.9Rows Larger Rows 1.0 orifice mm orifice mm diameter diameter 1.0 mm 1.1mm Shorter Shorter ori- orifice fice diameter diameter 0.85 mm 0.75 mmRemaining Remaining Remaining Remaining 40 Rows 31 Rows 40 Rows 31 RowsLarger ori- 0.8 mm Larger ori- 0.9 mm fice diameter fice diameter 0.95mm 1.05 mm Shorter ori- Shorter ori- fice diameter fice diameter 0.7 mm0.8 mm

As can be seen from Table 2 shown above, it may be understood that theprocess of the present invention allows to produce glass fibers withless fuel consumption for the equivalent production in quantity, and canimprove the compressive strength of the obtained glass fiber moldingwhen compared with the product produced according to the process of theprior art, and thereby, glass fibers capable of complying with qualityrequirement for medium-high glass fiber moldings can be obtained by thepresent invention.

For producing the low density glass fiber moldings, it is required toreduce the distribution of fiber diameters for ensuring good restoringproperty against compression. FIG. 7(a) shows the fiber diameterdistribution A of the low density glass fiber moldings obtained by theprocess of the present invention, to which the restoring propertyagainst compression is required. The fiber diameter distribution Arequired for the low density glass fiber moldings obtained by theprocess of the present invention is relatively narrow. FIG. 7(b) showsthe fiber diameter distribution B of the medium-high density productobtained by the process of the present invention, to which hardness andrigidity are required, and the fiber diameter distribution B is widerthan the fiber diameter distribution A of the low density product.Therefore, according to the process of the present invention, glassfibers having the fiber diameter distribution capable of complying withquality requirements for either of the low density products or themedium-high density products can be obtained.

As described above, according to the present invention, at least twotypes of orifices each having different diameter are provided in theperipheral wall of the rotating member alternately, and the primarystream of molten glass is ejected through the orifices by centrifugalforce, thereby allowing to form the fined secondary fibers of glass byintroducing the primary stream into the flame flow. The primary streamis fined into the secondary fibers, which can have a desired length bycolliding the secondary fibers with the compressed fluid from adirection at an acute angle. It is possible to easily obtain glassfibers with good quality capable of complying with various qualityrequirements, such as fiber diameter, fiber diameter distribution andfiber length, irrespective of the use for the low density product or themedium-high density product. In addition, the process of the presentinvention has further advantages of improving the production efficiency,reducing the fuel consumption for the drawing burner and therebyreducing the production cost.

Further, the apparatus according to the present invention allows toincrease the production of the secondary fibers with good quality bypreventing the collision of fibers at, the time of drawing into finefibers by means of alternately providing at least two types of orificeseach having a different diameter in the circumferential direction of theperipheral wall of the rotating member. Also, it is possible to operatethe processes from the primary stream to the secondary fiberscontinuously by a preventing to cause collision of the compressed fluidflow at the time of fining fibers by means of ejecting the compressedfluid from a direction at an acute angle against the flowing directionof the flame flow.

1. A process for producing glass fiber comprising: heating and rotatinga hollow cylinder-shaped rotating member having a peripheral wallprovided with orifices so as to rotate molten glass in the rotatingmember, and ejecting the molten glass through the orifices bycentrifugal force to form glass fiber, characterized in ejecting themolten glass through a larger orifice and a smaller orifice arrangedalternately in a circumferential direction of the rotating member in theperipheral wall, so as to form two types of primary streams havingdifferent length, introducing said primary streams into a flame flowaround the rotating member, said flame flow being ejected in a directionsubstantially parallel with a generatrix direction of an outercircumference of the peripheral wall, so as to fine said primary streamsto form secondary fibers, and ejecting compressed fluid in a directionat an acute angle relative to the flame flow including secondary fibers,to collide the secondary fibers with the compressed fluid so as to cutthe secondary fibers to control a length of the secondary fibers.
 2. Theprocess for producing glass fiber according to claim 1, wherein thecompressed fluid is ejected in an angle of 15-30 degree relative to thegeneratrix direction of the outer circumference of the peripheral wallof the rotating member.
 3. The process for producing glass fiberaccording to claim 1, wherein a distance between a top edge of thecompressed fluid and a bottom edge of the peripheral wall of therotating member is at least 30 mm.
 4. An apparatus for producing glassfiber comprising: a hollow cylinder-shaped rotating member having aperipheral wall alternately provided with a larger orifice and a smallerorifice in a circumferential direction of the peripheral wall, acircular drawing burner concentrically arranged above and around therotating member, and having an ejecting outlet opened in a directionsubstantially parallel with a generatrix direction of an outercircumference of the peripheral wall, and an ejecting nozzle around thedrawing burner, said ejecting nozzle being concentrically arranged aboveand around the peripheral wall of the rotating member, and having anejecting outlet opened in a direction at an acute angle relative to thegeneratrix direction of the outer circumference of the peripheral wall,wherein said peripheral wall has an upper side region and a lower sideregion, wherein said upper side region is alternately provided with thelarger orifice having a first diameter and the smaller orifice having asecond diameter in the circumferential direction, wherein said lowerside region is alternately provided with the larger orifice having athird diameter and the smaller orifice having a fourth diameter in thecircumferential direction, wherein said third diameter is smaller thansaid first diameter, and wherein said fourth diameter is smaller thansaid second diameter.
 5. The apparatus for producing glass fiberaccording to claim 4, wherein: the larger orifices are arranged in thegeneratrix direction of the outer circumference to form first bandsgroup of orifices, the smaller orifices are arranged in the generatrixdirection of the outer circumference to form second bands group oforifices, and the first bands group of orifices and the second bandsgroup of orifices are arranged alternately in the circumferentialdirection of the peripheral wall of the rotating member.
 6. Theapparatus for producing glass fiber according to claim 4, wherein adifference in the diameter between at least two types of orifices eachhaving different diameter is in a range of from 0.02 to 0.3 mm.
 7. Theapparatus for producing glass fiber according to claim 5, wherein adifference in the diameter between at least two types of orifices eachhaving different diameter is in a range of from 0.02 to 0.3 mm.
 8. Theapparatus for producing glass fiber according to claim 4, wherein thefirst diameter >the second diameter >the third diameter >the fourthdiameter.
 9. A process for producing glass fiber comprising: heating androtating a hollow cylinder-shaped rotating member having a peripheralwall provided with orifices so as to rotate molten glass in the rotatingmember, and ejecting the molten glass through orifices by centrifugalforce to form glass fiber, characterized in ejecting molten glassthrough a larger orifice and a smaller orifice arranged alternately in acircumferential direction of the rotating member in the peripheral wall,so as to form two types of primary streams having different length,introducing said primary streams into flame flow around the rotatingmember, said flame flow being ejected in a direction substantiallyparallel with a generatrix direction of an outer circumference of theperipheral wall, so as to fine said primary streams to form secondaryfibers, and ejecting compressed fluid in an angle of 15-30 degreerelative to the generatrix direction of the outer circumference of theperipheral wall of the rotating member, to the flame flow includingsecondary fibers, to collide the secondary fibers with the compressedfluid, so as to cut the secondary fibers to control a length of thesecondary fibers, wherein a distance between a top edge of thecompressed fluid and a bottom edge of the peripheral wall of therotating member is 30-50 mm.